Filayen
 Filayen | |
|---|---|
 | |
| Bayanai | |
| Ƙaramin ɓangare na |
plain (mul)  |
| Has cause (en) | zaizayar kasa |
A cikin ilimin ƙasa da ilimin ƙasa, peneplain wani fili ne mai ƙarancin ƙarfi wanda aka kafa ta hanyar rushewa mai tsawo. Wannan shine ma'anar a cikin mafi girman sharuɗɗa, kodayake tare da mitar amfani da peneplain yana nufin wakiltar matakin kusa da na ƙarshe (ko na ƙarshe) na rushewa ruwa a lokacin lokutan tsawo na kwanciyar hankali.[1] Ana danganta Peneplains a wasu lokuta da sake zagayowar ka'idar lalacewa ta William Morris Davis, [1] [2] amma Davis da sauran masu bincike sun kuma yi amfani da kalmar a cikin hanyar bayyanawa ba tare da wani ka'idar ko wani asali ba.
Tattaunawa
[gyara sashe | gyara masomin]
Kasancewar wasu peneplains, da peneplanation a matsayin tsari a cikin yanayi, ba tare da gardama ba, saboda rashin misalai na zamani da rashin tabbas wajen gano misalai masu mahimmanci.[1] Ta wasu ma'anoni, peneplains suna da matsayi har zuwa matakin tushe wanda ke wakiltar matakin teku, duk da haka a wasu ma'anar irin wannan yanayin an yi watsi da shi.[3] Masanin ilimin ƙasa Karna Lidmar-Bergström da abokan aiki suna la'akari da ma'auni na matakin tushe mai mahimmanci kuma sama da ainihin hanyar samar da peneplains, gami da wannan hanyar wasu pediplains tsakanin peneplains.[4][5]
Duk da yake ana zaton peneplains sun samo asali ne a kusa da matakin teku an kuma sanya cewa peneplains na iya samo asali a tsawo idan babban sedimentation ya ɗaga matakin tushe na gida sosai [6] ko kuma idan cibiyoyin sadarwar kogi suna ci gaba da toshewa ta hanyar lalacewar tectonic. [7] Yankunan Pyrenees da Tibetan Plateau na iya zama misali ga waɗannan lokuta biyu bi da bi.[6][7]
Wani kuskuren da aka saba da shi game da peneplains shine cewa ya kamata su kasance a bayyane ba su da alama. A zahiri, wasu peneplains na iya zama tuddai yayin da suke nuna yanayin yanayi mai zurfi, suna samar da daidaituwa zuwa matakin tushe kawai a babban sikelin.[4] [B]
A manyan sassan suna da halayyar bayyanar da aka sassaƙa a cikin dutse ba tare da la'akari da Tsarin dutse da lithology ba, amma a cikin daki-daki, ana sarrafa siffar su ta hanyar tsari, alal misali, rarraba ruwa a cikin peneplain na iya bin dutse mai tsayayya. A ra'ayi na Davis manyan rafi sun zama marasa tausayi ga lithology da tsari, wanda ba su kasance ba a lokacin kwarin kwarin na sake zagayowar rushewa. Wannan na iya bayyana wanzuwar koguna da aka ɗora.[8]
Nau'o'in peneplains
[gyara sashe | gyara masomin]Akwai kalmomi daban-daban don siffofin ƙasa waɗanda ko dai madadin ne ga peneplains na gargajiya, ƙananan ƙananan peneplains ko kuma wani ɓangare ya haɗu da kalmar. Na ƙarshe shine yanayin shimfidar wuri wanda zai iya zama peneplains ko a'a, yayin da wasu peneplains ba shimfidar wurare ba ne.[4]
A cikin aikin su na 2013 Green, Lidmar-Bergström da abokan aiki suna ba da tsarin rarrabuwa mai zuwa ga peneplains: [4]
- Yankin da aka tsara
- Mai tafiya
- Filin Inselberg
- Yankin da ke ƙasa
- Rashin tsaunuka Rashin tsaunin tsaunuka
- Yankin tsaunuka
Rhodes Fairbridge da Charles Finkl suna jayayya cewa peneplains sau da yawa suna da asali (polygenetic), kamar yadda za a iya tsara su ta hanyar etchplanation a lokacin yanayi mai zafi da pediplanation a lokacin yanayin busasshiyar yanayi. Tsawon lokaci wanda wasu peneplains ke tasowa yana tabbatar da Tasirin yanayi daban-daban.[2] Marubutan guda ɗaya sun kuma lissafa raguwar ruwa[C] da rushewar kankara tsakanin matakai waɗanda zasu iya ba da gudummawa wajen tsara peneplains.[2]
Bugu da kari, ana iya rarrabe epigene peneplains daga peneplains da aka tono.[4] Epigene peneplains sune wadanda ba a taɓa binne su ba ko kuma an rufe su da dutse mai laushi.[4][9] An gano wuraren da aka gano su ne waɗanda aka sake fallasa su bayan an binne su a cikin turɓaya.[4]
Tsohon peneplain da za'a iya ganewa a cikin yanki an san shi da peneplain na farko.[2] [D] Misali na farko peneplain shine Sub-Cambrian peneplain a kudancin Sweden.[10]
Tsuntsaye
[gyara sashe | gyara masomin]Ma'anar peneplain sau da yawa ana haɗa shi da na pediplain. Koyaya marubutan kamar Karna Lidmar-Bergström sun rarraba pediplains a matsayin nau'in peneplain.[4] Akasin haka Lester Charles King ya riƙe su a matsayin wuraren da ba su dace ba suna jayayya cewa ba su da fili. Sarki ya rubuta cewa: [11]
- Wani peneplain a cikin ma'anar Davisian, wanda ya haifar da raguwar gangara da raguwa, bai wanzu a cikin yanayi ba. Ya kamata a sake bayyana shi a matsayin "wani wuri mai ban mamaki".
A Sarki bambancin tsakanin pediplains da Davis" peneplains yana cikin tarihi da matakai a bayan kafa su, kuma ƙasa da haka a cikin siffar ƙarshe. Bambanci a cikin siffar da za ta iya kasancewa ita ce ta tsaunuka masu raguwa, waɗanda a cikin Davis" peneplains za su sami gangara mai laushi, yayin da a cikin pediplains ya kamata su sami irin wannan tsayi kamar gangara a farkon matakan rushewa wanda ke haifar da pediplanation.[12] Ganin cewa ƙuƙwalwar ƙuƙwalwa na pediplains sun samar da jerin gangaren ƙuƙwasawa masu laushi, bambanci da fahimtar Davis game da peneplains na iya kasancewa a cikin gaskiyar cewa ƙuɓɓugarsa masu laushi suna da gangaren ƙanƙara masu laushi a maimakon haka. Koyaya, ra'ayoyin Davis game da batun ba su da cikakkiyar fahimta.[12] Sabanin wannan ra'ayi Rhodes Fairbridge da Charles Finkl suna jayayya cewa ainihin tsarin samarwa (pediplanation, da dai sauransu) ba shi da mahimmanci kuma an yi amfani da kalmar peneplain kuma ana iya amfani da ita ta hanyar bayyanawa. Bugu da ƙari, sauyawa na matakai tare da sauyin yanayi, matakin teku na dangi da halittu suna sa tsoffin farfajiyoyi ba za su iya kasancewa na asali ɗaya ba.[13]
Tsaro da lalata peneplains
[gyara sashe | gyara masomin]
Ana gano filayen da aka raba daga matakin tushe ta hanyar karɓar bakuncin tarin turɓaya da ke binne shi ko kuma ta hanyar kasancewa a cikin matsayi mai tsawo. Kabari yana adana peneplain. Duk wani peneplain da aka fallasa daga tushe za a iya la'akari da paleosurface ko paleoplain.[4][15] Hawan farfadowa na peneplain yawanci yana haifar da sabuntawar lalacewa. Kamar yadda Davis ya sanya shi a cikin 1885: [16]
- "yanayin da ya lalace dole ne ya jira ko dai har sai an kashe shi ta hanyar nutsewa a ƙarƙashin teku, ko kuma ya sake farfadowa ta hanyar tsawo zuwa sabon zagaye na rayuwa".
Ana iya adana filayen da aka ɗaga a matsayin siffofin burbushin halittu a cikin yanayin matsanancin bushewa ko a ƙarƙashin kankara mai sanyi wanda ba ya rushewa.[4] Rushewar peneplains ta hanyar kankara a cikin yankunan garkuwar yana da iyaka.[17][18] A cikin Fennoscandian Shield matsakaicin rushewar kankara a lokacin Quaternary ya kai mita da yawa, kodayake wannan ba a rarraba shi daidai ba.[18] Don rushewar kankara ya zama mai tasiri a cikin garkuwar dogon "lokacin shiri" na yanayin da ba na kankara ba na iya zama abin buƙata.[17]
Silicification na saman peneplain da aka fallasa zuwa yanayin sub-tropical da na wurare masu zafi na tsawon lokaci na iya kare su daga rushewa.[17]
Manazarta
[gyara sashe | gyara masomin]- ↑ 1.0 1.1 1.2 Phillips, Jonathan D (2002). "Erosion, isostatic response, and the missing peneplains". Geomorphology. 45 (3–4): 225–241. Bibcode:2002Geomo..45..225P. doi:10.1016/S0169-555X(01)00156-8. Cite error: Invalid
<ref>tag; name "Phillips" defined multiple times with different content - ↑ 2.0 2.1 2.2 2.3 Fairbridge, Rhodes W.; Finkl Jr., Charles W. (1980). "Cratonic erosion unconformities and peneplains". The Journal of Geology. 88 (1): 69–86. Bibcode:1980JG.....88...69F. doi:10.1086/628474. S2CID 129231129. Cite error: Invalid
<ref>tag; name "FairFinkl1980" defined multiple times with different content - ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namedMigon - ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 Green, Paul F.; Lidmar-Bergström, Karna; Japsen, Peter; Bonow, Johan M.; Chalmers, James A. (2013). "Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins". Geological Survey of Denmark and Greenland Bulletin. 30: 18. doi:10.34194/geusb.v30.4673. Cite error: Invalid
<ref>tag; name "Greenetal2013" defined multiple times with different content - ↑ Lidmar-Bergström, Karna; Bonow, Johan M.; Japsen, Peter (2013). "Stratigraphic Landscape Analysis and geomorphological paradigms: Scandinavia as an example of Phanerozoic uplift and subsidence". Global and Planetary Change. 100: 153–171. Bibcode:2013GPC...100..153L. doi:10.1016/j.gloplacha.2012.10.015.
- ↑ 6.0 6.1 Babault, Julien; Van Den Driessche, Jean; Bonnet, Stephanie; Castelltort, Sébastien; Crave, Alain (2005). "Origin of the highly elevated Pyrenean peneplain". Tectonics. 24 (2): n/a. Bibcode:2005Tecto..24.2010B. doi:10.1029/2004TC001697.
- ↑ 7.0 7.1 Yang, Rong; Willett, Sean D.; Goren, Liran (2015). "In situ low-relief landscape formation as a result of river network disruption". Nature. 520 (7548): 526–530. Bibcode:2015Natur.520..526Y. doi:10.1038/nature14354. PMID 25903633. S2CID 1017663.
- ↑ Cite error: Invalid
<ref>tag; no text was provided for refs namedPalmquist - ↑ Twidale, C.R. (1985). "Old landsurfaces and their implications for models of landscape evolution". Revue de Géomorphologie Dynamique. 34: 131–147.
- ↑ Lidmar-Bergström (1988). "Denudation surfaces of a shield area in southern Sweden". Geografiska Annaler. 70 A (4): 337–350. doi:10.1080/04353676.1988.11880265.
- ↑ King, L.C. (1953). "Canons of landscape evolution". Geological Society of America Bulletin. 64 (7): 721–752. Bibcode:1953GSAB...64..721K. doi:10.1130/0016-7606(1953)64[721:cole]2.0.co;2.
- ↑ 12.0 12.1 King, L.C. (1953). "Canons of landscape evolution". Geological Society of America Bulletin. 64 (7): 721–752. Bibcode:1953GSAB...64..721K. doi:10.1130/0016-7606(1953)64[721:cole]2.0.co;2.
- ↑ Fairbridge, Rhodes W.; Finkl Jr., Charles W. (1980). "Cratonic erosion unconformities and peneplains". The Journal of Geology. 88 (1): 69–86. Bibcode:1980JG.....88...69F. doi:10.1086/628474. S2CID 129231129.
- ↑ Japsen, Peter; Green, Paul F.; Chalmers, James A.; Bonow, Johan M. (17 May 2018). "Mountains of southernmost Norway: uplifted Miocene peneplains and re-exposed Mesozoic surfaces". Journal of the Geological Society. 175 (5): 721–741. Bibcode:2018JGSoc.175..721J. doi:10.1144/jgs2017-157. S2CID 134575021.
- ↑ Bonow, Johan M.; Lidmar-Bergström, Karna; Japsen, Peter (2006). "Palaeosurfaces in central West Greenland as reference for identification of tectonic movements and estimation of erosion". Global and Planetary Change. 50 (3–4): 161–183. Bibcode:2006GPC....50..161B. doi:10.1016/j.gloplacha.2005.12.011.
- ↑ Orme, Anthony R. (2007). "The Rise and Fall of the Davisian Cycle of Erosion: Prelude, Fugue, Coda, and Sequel". Physical Geography. 28 (6): 474–506. doi:10.2747/0272-3646.28.6.474. S2CID 128907423.
- ↑ 17.0 17.1 17.2 Fairbridge, Rhodes W. (1988). "Cyclical patterns of exposure, weathering and burial of cratonic surfaces, with some examples from North America and Australia". Geografiska Annaler. 70 A (4): 277–283. doi:10.1080/04353676.1988.11880257. Cite error: Invalid
<ref>tag; name "Fairbridge1988" defined multiple times with different content - ↑ 18.0 18.1 Lidmar-Bergström, Karna (1997). "A long-term perspective on glacial erosion". Earth Surface Processes and Landforms. 22 (3): 297–306. Bibcode:1997ESPL...22..297L. doi:10.1002/(SICI)1096-9837(199703)22:3<297::AID-ESP758>3.0.CO;2-R.